The present invention relates in general to electric motors, and in particular to a bearing system and journal for the rotating output shaft of an electric motor.
Conventional electric motors include a rotating output shaft for driving a mechanical device. The output shaft is typically supported by a bearing mounted within an end frame of the motor for providing the drive shaft with a thrust surface. Known bearings include, for example, sleeve-type bearings and ball bearings. Ball bearings are generally more robust than sleeve bearings, and, therefore, are typically used in larger, more expensive motors. Sleeve bearings, on the other hand may be used in smaller motors, or lower cost applications.
Prior art motor end frame designs accommodate only one bearing type, e.g., either a sleeve or ball bearing, but not both. This significantly limits the design flexibility relative to the types of bearings which may be used. Essentially, to use an alternative bearing, an entire new end frame must be provided for receiving and properly supporting the new bearing type. Obviously, this is inefficient, costly, and time consuming.
Another difficulty associated with prior art bearing systems relates to the manufacturing steps required for assembling the bearing to the end frame. Typically, a bearing, e.g., a sleeve bearing, is secured to the end frame using multiple parts, which may require permanent affixation, e.g., by welding. The multiple parts and manufacturing steps add to the manufacturing cost and, ultimately, to the end cost of a user.
Accordingly, there is a need in the art for an efficient and reliable bearing system which allows use of a sleeve or ball bearing in the same end frame. There is also need in the art for a sleeve bearing system which includes a minimized part count and which requires no fasteners during assembly.
Thus, the present invention is organized about the concept of providing a bearing system which may incorporate either a sleeve or a ball bearing, provides a minimized part count, and requires no fasteners for assembly, while providing for oil recirculation. The assembly includes a bearing journal having a sleeve bearing portion and a ball bearing portion. Where a sleeve bearing is used, a first end of the sleeve bearing is supported in the sleeve bearing portion of the journal, and a second end of the sleeve bearing may be supported by a finger spring. The sleeve bearing and finger spring are retained within the journal by an end cap which may be press-fit into the ball bearing portion of the journal. Where a ball bearing is used, the ball bearing may be press fit directly into the ball bearing portion of the bearing journal, or press fit into a spacer which is press fit into the ball bearing portion of the bearing journal.
More particularly, according to the invention there is provided a bearing journal including a sleeve bearing portion adapted for supporting a sleeve bearing and a ball bearing portion adapted for supporting a ball bearing. In one embodiment, the sleeve bearing portion is generally frusto-conical in shape and is defined by a sidewall and an end wall. An interior surface of the sidewall is adapted for contacting a first end of the sleeve bearing for supporting the sleeve bearing in the sleeve bearing portion. In another embodiment, the sleeve bearing portion is defined by a sidewall and an end wall, and a plurality of inwardly extending tabs are disposed on an interior surface of the side wall. The inwardly extending tabs are adapted for contacting a first end of the sleeve bearing for supporting the sleeve bearing in the sleeve bearing portion. Preferably, the sleeve bearing portion has an end wall and is adapted for supporting the sleeve bearing with a space between an end surface of the sleeve bearing and the end wall. The space may be filled with an oil medium for lubricating the bearing.
The ball bearing portion may be generally cylindrically shaped, and may be dimensioned to receive a ball bearing directly therein with a press-fit. Alternatively, the ball bearing portion may be dimensioned to receive a spacer directly therein with a press-fit. The ball bearing may be press-fit directly into the spacer.
In an embodiment of a bearing system according to the invention where a sleeve bearing is used with the bearing journal, the sleeve bearing may have a first end and a second end with the first end supported in the sleeve bearing portion of the journal. A finger spring may be disposed in the bearing journal for supporting the second end of the sleeve bearing. The finger spring may be generally annular having a radial flange and plurality fingers extending downwardly and radially inwardly from an inner edge of the radial flange. The second end of the sleeve bearing may be supported by the finger spring with the plurality of fingers in contact with the sleeve bearing. In another embodiment, the finger spring may be generally frusto-conical in shape having a radial flange, a frusto-conical sidewall extending from the flange, and an end wall. The second end of the sleeve bearing may be supported by the finger spring with the frusto-conical sidewall in contact with an exterior surface of the sleeve bearing, and the end wall in contact with an end surface of the sleeve bearing.
The exterior surface of the sleeve bearing may have oil recirculation channels disposed therein which provide space for an oil medium to travel between spaces adjacent to the first end of the sleeve bearing and the second end of the sleeve bearing.
An end cap may also be provided for securing the sleeve bearing and the finger spring in the bearing journal. The end cap may be press-fit into the bearing journal, e.g., with a first portion of the end cap in pressing engagement with an interior surface of the ball bearing portion. The end cap may be generally cylindrical in shape, and may have an end surface which contacts the finger spring to secure the finger spring and the sleeve bearing within the bearing journal.
Various other features, objects and advantages of the invention will be made apparent from the following description taken together with the drawings.